Most known light sources have incandescent lamps, arc lamps or high-pressure lamps. During the operation thereof, a relatively large proportion of electrical energy is converted into heat, which may be problematic for surrounding devices or components. In this case, in order to generate light of a specific colour locus on the international standard CIE (International Commission on Illumination) chromaticity diagram, use is generally made of optical filters in order to eliminate undesirable colour components to the greatest possible extent. However, this reduces the efficiency of the respective light source.
As an alternative, there are light sources which use light-emitting diodes (LEDs), which have for example the advantage of a long service life, a fast response and also a relatively high electrical efficiency. Moreover, polychromatic light of a specific colour locus can be generated by combining LEDs of different colours. Colour filter are not absolutely necessary in this case.
A light source for the backlighting of an LCD display, said light source having LEDs with different emission spectra, is described in U.S. Pat. No. 6,540,377 for example, in which red-, green- and blue-emitting LEDs are arranged in a manner intermixed with one another on a common plane. During operation of the light source, the electromagnetic radiation of the LEDs is radiated in a common light cone and intermixed by means of diffusor material.
One disadvantage of such a light source is that the light intensity that it radiates per solid angle is limited by the maximum emission intensity of the LEDs, as a result of which its applicability is restricted. Moreover, it is necessary to provide for sufficient intermixing of the electromagnetic radiation emitted by different LEDs if homogeneous light is desired.